Methods of making reinforced plastic sheeting



0a. 20, 1970 G. P. GASAWAY 3,535, 8

METHOD OF MAKING REINFORCED PLASTIC SHEETING Filed Feb. 28. 1967'IIIIIIIL'I4VIIIIII. 4 [III/III;

W W M 5, m y mulmm m m Am rvw 7 United States Patent 3,535,180 METHODSOF MAKING REINFORCED PLASTIC SHEETLNG Glen P. Gasaway, Buford, Ga.,assignor to Johnson & Johnson, a corporation of New Jersey Filed Feb.28, 1967, Ser. No. 619,309 Int. Cl. B32b 5/08 US. Cl. 156178 4 ClaimsABSTRACT OF THE DTSCLOSURE Plastic sheet material comprising a textilelattice of coated intersecting yarns which are coating-fused at theirintersections and are engulfed by layers of plastic materials on bothsides to provide an essentially moistureimpervious reinforced laminatedstructure, and improved methods of making the same.

This invention resides in a plastic sheeting reinforced by an internalnetwork of traversing coated yarns fused at their points ofintersection.

Many reinforced sheet materials have been developed for utilization asbarriers against the weather, and specifically as moisture barrierguards in many areas. Additionally, such sheeting has been visualized asa barrier guard against the elements of nature where no truly dependableguard now exists for certain contemplated uses, especially in theconstruction field.

Of the many products that have been produced for these intendedpurposes, it has been found that each has been lacking in one or more ofthe properties defined by a bursting strength, water impermeability,tear resistance and tensile strength, where these properties are factorscombining to provide the needs and requirements of sheeting materials ofthis nature.

These and other problems have been overcome by the instant inventionwhich furnishes a textile lattice of traversing thermoplastic coatedyarns, coating-fused at their points of intersection, said lattice beingintegrally engulfed by a plastic layer to provide an essentiallymoisture impervious, reinforced plastic sheet having a burst strength ofat least about 130 pounds per square inch.

Textile lattice as used herein shall mean both woven textile fabricwhere warp and filling yarns are interlaced, e.g., scrim or gauze, andunwoven mats or layers where a first set of yarns having each yarnarranged in a spaced, parallel relationship, is positioned under or ontop of a second set of yarns arranged in a similar manner such that theyarn of one set is angularly' disposed with respect to the yarns of thesecond set. The constructions of the woven fabrics shall range fromabout 4 x 4 to about 20 x 20 to provide an open construction and themats or layers of unwoven crosslaid yarns shall have equally openconstruction ranges.

Construction of less than 4 x 4 are too open to contribute less than theminimum values for the essential physical characteristics such astensile and bursting strengths which are required of the reinforcedplastic sheet of fabric of this invention, and constructions of greaterthan 20 x 20 are too tight to allow the plastic layer engulfing thetextile lattice to enter the interstice between adjacent yarns to insureintimate contact between the plastic layer and the coated yarns alongthe entire surface area of each yarn. Thus, constructions tighter than20 x 20 allow the formation of voids within the plastic layer. Theformation of such voids would encourage yarn movement within the plasticsheeting and thus act to diminish the over-all burst strength of thesheeting. Such a circumstance would also contribute to localizedreduction in tear strength and tensile strength and thus reduce theoverall elfectiveness of the sheet to a value below that desired andthat which is characteristic of this invention.

The yarns forming the textile lattice of this invention must have atensile strength of at least about 40,000 psi. and must be constructedof synthetic or metallic filaments having a breaking tenacity in the wetstate of at least about 5 pounds when tested in accordance with ASTMD578. The yarn used herein should be resistant to solutions of mostacids and alkalies, should not be affected by common organic solventsand must be resistant to attack by mildew.

The invention will be more readily understood by reference to thefollowing detailed description taken in conjunction with the attacheddrawing in which:

FIG. 1 is a plan 'view of one embodiment of a textile lattice of thisinvention,

FIG. 2 is a plan view of the reinforced plastic sheet of this inventionbroken away to show its construction,

FIG. 3 is an enlarged view of two traversing coated yarns of thisinvention with sections broken away to show more revealing detail,

FIG. 4 is an enlarged cross section taken along 44 of FIG. 3,

FIG. 5 is an enlargement of FIG. 4 broken away to avoid unnecessaryduplication, and

FIG. 6 is a diagram illustrating steps in the process of making theproduct of this invention.

With specific reference to FIG. 1 there is shown a textile lattice 1 oftraversing coated glass yarns 2, coatingfused at their points ofintersection. The coated yarns 2 are seen to be divided into two sets,each set consisting of parallel, spaced yarns which are, in thisinstance, interwoven, i.e., the yarn of one set are interwoven with theyarn of the other set, to provide on open scrim of warp (one yarn set)and filling yarns (the other yarn set). The yarns consisting of thesubstantially equally spaced parallel yarns which define a first set ofcoated yarns 2a could equally as well be angularly positioned atop, orbelow, the second set of substantially equal spaced parallel coatedyarns 2b which define the second set of yarns. The angle at which theyarns of either set cross of interlace is not important; however, it ispreferred that the yarn of one set is positioned to traverse yarn of theother set at substantially right angles.

FIG. 3 is an enlargement showing two yarns 2a and 2b of the lattice '1of FIG. 1 which traverse and are coating-fused at 3. The coated yarn 2is seen to consist of a glass multifilament twisted yarn 4 coated with aplastic material 5 Which in this instance shall be heat and ultravioletlight stabilized vinyl chloride. The yarns are each cut away in part atthe point of intersection 3 to show the coating-fused nature of the bondefiected between these two yarns at that point. Note that the fusion isbetween the coatings 5 on each yarn but that a width of yarn-coatingplastic 5 separates the glass core yarn 4 of each coated yarn 2. This isvery important and is essential to the instant invention.

The fusion of yarn coatings 5 of each coated yarn 2 at their points ofintersection stabilizes the textile lattice 1 and prevents yarn movementto provide stability and strength to the lattice 1. The fact that thefusion is a coating-fusion is very important since it prevents intimatecontact between the yarn 4 of each coated yarn 2. If such intimatecontact of yarn 4 with yarn 4 was permitted, abrasion through use wouldsoon cause severance of yarn at this point, resulting in failure of thereinforced sheeting of this invention.

FIG. 2 depicts the plastic sheet 7 of this invention in cutaway in orderto show in detailed construction whereby the textile lattice 1 of FIG. 1is integrally engulfed 3 by plastic sheeting 6 which may consist of twofilms or sheets of plastic material 6a and 611 shown in cutaway here.The lattice 1 is a complete internal structure as to the sheeting 6since the plastic sheeting spans each of the interstices betweenadjacent yarns 2 of the lattice 1 and completely envelopes each coatedyarn 2 along its entire length and surface in a manner such as topreclude a space or void separating the surface of the coated yarn 2from the plastic sheeting 6.

FIG. 4 is an enlarged cross section taken along line 44 of FIG. 2. Theyarns 2a of one set are seen to traverse one yarn 2b of the other set ofyarns in the textile lattice 1. The completeness of the coating of theplasitc sheeting 6 within the interstices between adjacent yarns isshown in detail.

FIG. 5 is the cross section of FIG. 4 much enlarged and broken away toavoid unnecessary duplication. Note that the glass core 4 of core yarn2a is completely surrounded by an intimate uniform coating 5a of plasticmaterial, e.g., polyvinyl chloride. The same is true of core yarn 2bwhich has the intimate coating 51; of polyvinylchloride film. Note alsothe nature and character of the coating-fused intersections between thetraversing yarns 2a and 2b. There is a sufficient thickness of coatingmaterial 5 between the core of these traversing yarns to precludecontact between the glass cores 4 of these yarns. Also because of thiscoating-fusion, lateral or lengthwise movement of the yarns 2a or 2b isnot permitted and strength and stability are built into the finishedproduct.

Preferably the reinforced plantic sheeting 7 is produced via the processshown by FIG. 6 Where a woven scrim 8 of coated glass yarn,coating-fused as shown in FIG. 2, and a thermoplastic sheet material 11join in facewise engagement before the scrim enters the nip betweenrolls 9 and 10. Just prior to the entrance of sheet 11 and scrim 8between the nip between the rolls 9 and 10, molten thermoplasticfilm-forming material 12 is deposited onto the surface of the scrim 8 asit forms a composite with sheet 11. The mass comprising the scrim 8, thesheet 11 and the layer of thermoplastic film-forming material then allpass between pressure rolls 9 and 10 and the latter press thesecomponents together with sufficient pressure to cause the moltenthermoplastic material 12 to be fused directly to thermoplastic sheet11, substantially entirely throughout each of the interstices betweenadjacent coated yarns 2 defining the scrim 8.

While pressure is being applied to the partially hardened thermoplasticfilm-forming material 12, it is further cooled by pressure roll 10 sothat, in addition to being bonded to the thermoplastic material 12, itbecomes further hardened so as to define (with sheet 11) a commonplastic sheeting 6 completely engulfing the scrim 8. The reinforcedplastic sheet 7 made up of the fused together thermoplastic film-formingmaterial 12 and the thermoplastic sheet 11 which sandwich the wovenscrim 8 is led from the cooling pressure roll 10 over an idler roll 13as a finished product. The reinforced plastic sheeting may be wound upon a roll up winder 14, or the like.

The gauge, or the thickness, or the composite sheet material consistingof 11 and 12 depends upon the end use of the reinforced sheet material7. However, merely by way of example, the gauge may be approximately 15mils. As a minimum, there must be substantially uniform thickness of atleast 8 mils spanning the interstices between adjacent yarn of the scrimand a thickness of at least about 15 mils of composite sheet material 11and 12 covering the coating 5 of each yarn 2. Thus in the process shownvia FIG. 2, the thermoplastic sheeting 11 must have a thickness of atleast about 4 mils.

Pressure roll 9 has a resilient surface and is preferably made ofrubber, e.g., foamed rubber. Pressure roll 10 is made of steel or someother suitable metal and is chilled by suitable means not shown. Eachroll has a length predetermined according to the desired width of thefinished product. Roll 9 is biased against roll 10 with suflicientpressure to cause the solid sheet of thermoplastic 11 to be forcedagainst the already surface-cooled film or sheet of thermoplasticfilm-forming material 12 on pressure roll 10 during the hardening of thecenter portion of the film, after which it may be stripped from roll 10.By way of example, rolls 9 and 10 may exert a nip pressure in theneighborhood of thirty to sixty pounds per linear inch on the materialpassing between the rolls without extruding or squeezing out the freshlyhardened film 12 from between roll 10 and the mesh fibers.

The substantially molten thermoplastic film-formin g material 12, e.g.,polyethylene, is poured or extruded in sheet or laminate form from anorifice 14 of a suitable linear nozzle or die, indicated generally bythe reference numeral 15. In the case of polyethylene, as it leaves theorifice 14, it is at a temperature in the range of from 400500 F. and istherefore more fluid than solid but has a degree of tensile strengthsufficient to maintain uniform surface in the absence of formingpressure. Extruder head 15 has an orifice 14 in the form of a slit ofcontrolled width extending along the length of either rolls 9 or 10 andclose to the surface of scrim 8. The illustration of FIG. 6 is schematicand the orifice 14 would normally be placed very near to the point ofcontact of film 12 with roll 10 for better control of film temperature.

It should be understood that the finished reinforced plastic sheeting 7could be cast of two hot fluid sheets of thermoplastic material 12engulfing the coated yarns of the textile lattice 1 by the use of tworolls such as 10 except that one roll must have a resilient surface toaccommodate the mesh under pressure and prevent the formation of thinspots in the plastic sheeting 6a and 6b of FIG. 3 which would form atthe points of yarn intersection if two hard surface rolls were used andto also preclude the possible destruction of the coating-fusion both atthe yarn intersection and even the thinning or even the destruction ofthe yarn-coating thickness between intersecting yarns at points of yarntraversal in the lattice 1. The use of two rolls such as 9 isunsatisfactory since a flexible roll of foamed plastic or the like wouldnot provide the very rapid cooling needed in a high speed process.

The synthetic coating 5 applied to the core yarn of glass (monofilamentor multifilament), or metal multifilaments, or of other suitablematerials, must have a melting point, or a softening point, suflicientlyremoved (below) the melting point of the core yarn 4, to permit thecoating of the yarn without causing melting or surface tackiness of thecore yarn 4 or of the filaments which compose it, such as to diminishthe strength, flexibility, etc., of the yarn 2. Thus the yarn-coatingmaterial 5 must have a melting point below about 300 F. however, themelting point of this yarn-coating material must also be suflicientlyhigher than the melting point of the sheeting material 6 which engulfsthe entire textile lattice, to permit its deposition on the textilelattice of coated yarn without destroying the integrity of the coatingmaterial 5, or seriously diminishing its thickness, which thicknessshall be substantially uniform and within the range of from about 3 toabout 5 mils.

The requirements of the yarn used herein were given earlier, and it hasbeen stated that the yarn-coating material, which is applied by normalmethods, e.g., extrusion coating, must have a melting temperaturesufliciently below the melting point of the yarn it is to coat, and ofthe filaments comprising the yarn. This is necessary to preventdiminution of the strength, flexibility, etc., which are built into theyarn. However, this synthetic yarncoating material must also have highstrength, abrasion resistance, good resilience and flex life. The flexlife is important since the yarn meeting the physical and chemicalrequirements specified herein will ordinarily have poor flex life andthe yarn-coating material will act to contribute measurably to the flexlife of the yarn it coats.

The yarn-coating material must have good abrasion resistance andstrength since the core yarn must not be able to cut through theircoatings to meet the exposed surface of the yarn it crosses at traversalpoints in the scrim. If this were to happen, the abrasion resultingthrough normal use of the reinforced plastic sheeting would causeseverance of the core yarn at these points and the formation of weakspots dependent solely on the strength of the over-all plastic coatingwhich contains or engulfs the textile lattice. The burst strength of thefinished sheet at these points would be considerably lower than theminimum required herein.

Preferably, the yarn-coating material is chosen from the vinyl or theacrylic polymeric materials, but most preferably it is polyvinylchloride.

The plastic materials 11 and 12 providing the overall cover or coatingto the textile lattice, shall have a melting point, or melting points,below that of the yarn-coating material, i.e., below 300 F. Theseplastic textile latticecoating materials must also be capable ofproviding a water impervious film or sheeting which is resistant to theaction of fungi and other common organisms which would act to destroy orpenetrate such a film and must also have a good flexibility since itcontributes meaningfully to the flexibility of the reinforced plasticsheeting of this invention which is characterized as having a goodflexibility. Of course, by varying the flexibility of the plasticmaterials, the flexibility of the reinforced sheet can be predicablyaltered. The reinforced plastic sheeting of this invention is capable oftaking large strains without fracture and without excessive permanentdeformation even at temperatures as low as F. It should also have goodabrasion resistance and good resistance to the transmission of anelectrical current. It should also exhibit good resistance to weak acidsand bases.

As has been mentioned, the plastic sheeting which coats and contains thetextile lattice may be applied as a sandwich of two films {when heat isused to make either, or both, sheet tacky), where the lattice is betweenthese two sheets, and the reinforced sheeting may also be formed bysandwiching the lattice between a sheet and a hot or moltenthermoplastic film-forming material and cooling or by utilizing anapplication of a molten thermoplastic film-forming material to bothsurfaces of the film. However, the plastic sheet material used may bethe same for coating both surfaces of the lattice or they may differ solong as they will fuse together strongly at a temperature significantlybelow the melting point of the yarn-coating material.

The plastic sheeting may tightly engulf the coated yarn forming thelattice without fusing to the surface of the yarn-coating material but,because of its tight and complete engulfment, on cooling it must remaincompletely contiguous to the yarn coating throughout the lattice, andthus strongly physically positioned and devoid of spaces between theyarn coating and the lattice sheeting. It may also fuse lightly to theouter surface of the yarn-coating material to provide a fusion bond. Thenature of the relationship depends on the materials chosen. Polyethyleneis preferred.

The reinforced plastic sheeting according to this invention is waterimpervious and not attacked by fungi. It has a burst strength of atleast about 130 pounds per square inch (ASTM D77463T), a tensilestrength of at least about 85 pounds (ASTM D1682-64) and a tearingstrength of at least about 7 pounds measured in the direction of eitherthe warp or the fill (ASTM D39-61, Tongue Method). It also exhibits awater vapor transmission rate utilizing Procedure B of ASTM E96-63T,i.e., 100% relative humidity one side of the sheet and 50% relativehumidity at 73 F. on the other side of the sheet, of less than about0.05 grain per hour per 100 square inches of sheeting and, utilizingProcedure E, i.e., 0% relative humidity on one side of the sheet and 90%6 relative humidity at F. on the other side of the sheet of less thanabout 0.10 grain per hour per 100 inches of sheeting.

It is most important to note that the yarns of the textile lattice arewholly contained by plastic sheeting, and do not separate at theirtraversal points, and these yarns do not move laterally within theplastic sheeting.

Reinforced plastic sheeting according to the present invention isnormally clear and translucent; however, if desired, it may be coloredor may be made opaque by the use of suitable pigments. Additionallycompatible heat stabilizers, antioxidants and ultraviolet stabilizers(such as those disclosed in copending patent application Ser. No.341,614) etc., may be added.

A few of the many uses for this sheet material are as a glass substitutefor window openings, particularly in greenhouses; as tarpaulin materialfor covering machinery, etc., as a ground covering for nurseries, as abarrier material placed under plastic floors and generally in otherareas of the construction industry as a strong barrier against moisture.

While I have described and illustrated a preferred embodiment andpractice of this present invention, I wish it understood that there isno intention to employ such restrictions but rather that allmodifications thereof which would be apparent to one skilled in the artand which come within the sphere and scope of the appended claims are tobe included.

What is claimed is:

1. The method of making a reinforced plastic sheet material whichcomprises the steps of coating yarns with a plastic, forming a textilelattice of said coated yarns and fusing said coated yarns at theirintersections to form a fused lattice, laying said fused latice onto apreformed sheet of plastic material, extruding a semimolten film of aplastic material onto said preformed sheet of plastic material and oversaid lattice, cooling a surface of said film sufficiently to form asolid film surface prior to application of laminating pressure, andpressing said lattice and plastic materials together to sandwich saidlattice between said materials, thereby to bond said plastic materialsto said lattice substantially entirely throughout each opening of saidlattice to provide a reinforced plastic sheet having a burst strength ofat least about pounds per square inch and a tear strength of at least 7pounds.

2. The method of making a reinforced plastic sheet material as definedin claim 1, wherein the coated yarns are coating-fused together at theirintersections without creating intimate contact between their respectivecore yarns whereby abrasion between said respective core yarns isprecluded.

3. The method of making a reinforced plastic sheet material as definedin claim 1, wherein the coating-fusing at the intersections of thecoated yarns of the textile lattice takes place at a higher temperaturethan the temperature of the subsequent bonding of the plastic materials,whereby the coating-fusion is relatively unaffected by said subsequentbonding.

4. The method of making a reinforced plastic sheet material as definedin claim 3, wherein the bonding of the plastic materials takes place ata temperature below about 300 F.

References Qited UNITED STATES PATENTS 3,442,750 5/1969 Wilcox l56l78 X3,444,024 5/1969 Hillas 156-178 X 3,444,025 5/1969 Hillas l56--l78 XCARL D. QUARFORTH, Primary Examiner S. I. LECI-IERT, JR., AssistantExaminer US. Cl. X.R. l56l8l, 244, 306

